Aluminum electrical connection

ABSTRACT

This invention relates to a connector for electrical conductors and more particularly to a connector adapted to receive aluminum and copper conductors therein. The connector includes an elongated groove wherein the inwardly facing edges of the sidewalls defining the grooves provide a scraping action against the conductor to break up the oxide film or insulation thereon and further wherein the sidewalls are elastically flexed outwardly by the tamping of the conductor into the groove so as to maintain a continual pressure on the conductor and thereby counter creep induce by temperature change and the like.

- [22] Filed:

United States Patent [1 1 Ziegler, Jr. et al.

[ 1 ALUMINUM ELECTRICAL CONNECTION [75] Inventors: George William Ziegler, Jr.,

Carlisle; Henry William Demler, Jr., Lebanon, both of Pa.

[73] Assignee: AMP Incorporated, Harrisburg, Pa.

Sept. 4, 1973 [21] Appl. No.: 393,841

Related U.S. Application Data [63] Continuation-impart of Ser. No. 320,021, Jan. 2,

1973, Pat. No. 3,777,051.

[52] U.S. Cl 174/94 R; 29/628; 174/72 R; 339/97 C; 339/276 R; 339/276 T [51] Int. Cl H02g 15/08 [58] Field of Search 174/84 C, 90, 94 R, 71 R; 29/628, 630 F; 339/276 R, 276 T, 223 R, 97

[111 3,878,318 [451 Apr. 15, 1975 3,777,051 12/1973 Ziegler, Jr. et al 174/84 C X Primary Examiner-Darrell L. Clay Attorney, Agent, or FirmAllan B. Osborne, Esq.

57 ABSTRACT This invention relates to a connector for electrical conductors and more particularly to a connector adapted to receive aluminum and copper conductors therein. The connector includes an elongated groove wherein the inwardly facing edges of the sidewalls defining the grooves provide a scraping action against the conductor to break up the oxide film or insulation thereon and further wherein the sidewalls are elastically flexed outwardly by the tamping of the conductor into the groove so as to maintain a continual pressure on the conductor and thereby counter creep induce by temperature change and the like.

1 Claim, 17 Drawing Figures ALUMINUM ELECTRICAL CONNECTION CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part application of Ser. No. 320,021, filed Jan. 2, I973, and now US. Pat. No. 3,777,051.

BACKGROUND OF THE INVENTION The connection of an electrical conductor to a connector by tamping the conductor into a groove in the connector is taught in US. Pat. No. 3,038,958 issued to R. C. Swengel, the disclosure of which is incorporated herein by reference.

As pointed out in Swengel, good results are obtained if the wire is of soft copper and the connector is of brass or steel. Recently. increased attention is being given to the use of aluminum conductors, particularly in industrial construction, mobile homes, modular housing and the like. A problem with the use of aluminum conductors, however, is that of terminating them to achieve superior electrical and mechanical junctures. It was found that the aluminum conductor would break in the area immediately adjacent to the end of the connector after very little bending due to the abrupt transition from the configuration of the wire in the groove to the round shape.

Accordingly, it was an object of the invention disclosed in the aforementioned application to provide a grooved aluminum connector adapted to receive aluminum conductor therein so that from 70 to 100 percent of the conductor is tamped within the groove and further that there is a gradual transition zone between the connection and the non-deformed conductor. Additional work, however, has disclosed the fact that the gradual transition zone is not necessary in some specific applications. Accordingly it is an object of the present invention to disclose a connector wherein the transition zone is not a requirement for achieving an electrical connection which satisfies industry standards therefor. Further, it is an object herein to disclose a connector suitable for jointly terminating stranded cop per fixture wire and solid aluminum house wire.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I, a wire with its insulation I2 stripped back away from aluminum conductor 14 is ready for connection to aluminum connector 16 which is shown directly below the conductor.

Connector 16 includes at its front end 18 a conventional ring tongue 20. it is to be understood that the front end is not part of this invention and will not be further described.

The backend 24 of connector 16 includes a conductor-receiving groove or channel 26 which is defined by sidewalls 28 and floor 30.

As seen in FIG. 1, sidewalls 28 are positioned from about to 80 relative to floor 30 with the preferred angle being about This structure provides a generally trapezoidal shape to channel 26 as can be seen in FIG. 3. The radius of the intersection of sidewall 28 and floor 30, designated in FIG. 3 by R is preferably rounded. The edges 32 between the inner surface 28a of sidewalls 28 and top surface 34 are preferably sharp so that as the conductor is pressed into channel 26, the oxide film or insulation thereon can be scraped away to provide a better electrical contact between the conductor l4 and connector 16.

Because of edges 32 being preferably sharp, some of the conductors 14 will be peeled back as the conductor is pressed into channel 26. This peeled material forms a crown 36 which amount should be kept as small as possible. However, in order to insure that channel 26 is filled completely with conductor 14, the crosssectional area of channel 26 is made to be slightly less than the cross-sectional area of conductor 14. Thus. for a conductor having a diameter d, the cross-sectional A of channel 26 is:

A .20mF

Theoretically, the above formula would result in all but 20 percent of conductor 14 being received into channel 26. As a practical matter, as the conductor is tamped into the connector, sidewalls 28 are elastically deformed laterally with the result that the channel will accommodate up to another 10 percent of the conductor.

The importance of having at least percent of the aluminum conductor within channel 26 is that there must be as much interfacial contact between the conductor and connector as possible. Obviously. the more interfacial contact thereinbetween, the higher the conductivity and less susceptability to attack by corrosion. Experiments have shown, however, that there are primary contact areas without which suitable conductivity is not achieved. These primary contact areas are on the upper sides of the sidewalls 28 in the vicinity of edges 32 and adjacent thereto. Such areas are designated generally at 37 inFIG. 3. A secondary contact area exists on the floor30 of channel 26.

Although the cross-sectional area of channel 26 is preferably about 80 percent of the conductor being positioned therein, testing has shown that satisfactory electrical connections are obtained where the area of the channel varies from about 60 to about I20 percent of the conductor. The importance of this is that one size connector is capable of terminating a wide range of wire sizes.

In order to size the opening of channel 26', i.e., the width between edges 32, so as to achieve the aforementioned peeling, the following formula may be used:

where W is the width and d is the conductor diameter.

The thickness of sidewalls 28 may be kept thin; however, a minimum thickness is required so that as conductor I4 is being tamped in, the aforementioned deformation does not exceed the yield strength of the aluminum. Experimental data suggests that the optimal sidewall thickness be one-half d for conductors larger than AWG and one-third d for conductors equal to or smaller than 10 AWG. This optimal thickness is not so critical however that a connector of given size cannot receive different wire sizes.

FIG. 2 illustrates connection 35 made between conductor l4 and connector 16. The pressing or tamping of conductor 14 into channel 26 is achieved by means of a suitable tool member 40 seen in FIG. 4.

FIG. .2 illustrates the important transition zone 38 which occurs between the deformed or tamped portion of conductor 14, hereinafter designated at 140, and the non-deformed portion hereinafter designated at 14b. The transitional zone 38 comprises the top transition 38a and the lower transition 38b which is on connector 16. Both are formed as a result of the rounding or bevelling of dies 44 which can be seen in FIG. 4a and to which references will be made below. it has been found that with a sharp demarcation; i.e., no transitional zone, excessive stresses in a terminated conductor are present at that point and that breakage thereat occurs under mild bending tests. A gradual transition zone on the other hand eliminates the internal stresses and the flexibility of the connection is greatly enhanced; i.e., wire 10 maybe ,moved relative to the connection a substantial number of times before breakage occurs at the juncture. Testing subsequent to the filing of the aforementioned application Ser. No. 320,021 has shown that the two transitional zones, 38a and b can be eliminated in some ;cases.iThis is particularly true in the case of a splice such as shown in FIGS. 5 and 6. Further in case where the-connection is insulated, stresses are shifted -'fromthe edge of the connector to the trailing edge of the insulation.

'In the finished connection which is seen in crosssection in FIG. 3, conductor 14 contained in channel 26 is retained therein by the inwardly pinching action of the stressed sidewalls 28, Le, the sidewalls are cona tinually being urged against the conductor 14. An important advantage of this, which is well known to those skilled in the art, is that should the conductor undergo -imetallic creep during the life of the connection, the

sidewalls 28 follow the wire by moving relatively towards-each other. In this manner an intimate contact is constantly maintained. 3

FIG. 3 also shows how conductor 14 is extruded into all parts of channel 26 so as to completely fill the channel and thereby decrease or eliminate the likelihood of corrosion therein.

FIG. 4a illustrates the two piece tool member 40 with a connector 16 placed inbetween anvil member 42 and "nest member 44. Both the anvil and nest members have on their connector-engaging surfaces 46-48 respectively,-gently-sloping ends 50-52. As FIG. 4b shows sloping end 50 on anvil 42 provides top transition 38a. The width of anvil 42 is no wider than the distance between edges 32 and preferably is slightly smaller. As the anvil is pressed down, most of its force is directed against the floor of connector 16 through conductor 14. Sloping end 52 in conjunction with surface 48 on nest 44 provides lowertransistion 38b onto connector 16 by bending back end 24 downwardly away from conductor 14. The amount'of separation is slight. only enough to allow some freedom of movement of conductor l4.relative to the connector.

The versatility of the present invention can be seen in the variety of uses described hereinafter. As willbe apparent, all the fundamental advantages are common to all embodiments.

Referring now to FIG. 5, an embodiment'is shown which permits a splicing together of two separate conductors 14. The connector 60 may be cut to length to fit whatever space is available, such shortening having no detrimental effects on the mechanical connection. However. for good electrical connections, the length of channel 26 which receives conductor 14 should preferably be not less than about three or more wire diameters.

FIG. 6 shows a commoning bar accommodate having double channels 26. As shown, bar 62 can accomodate a number of connections 64. This embodiment illustrates a case wherein lower transition 3817 was found not to be required. In tests based on Underwriters Labs standards, the embodiment was subjected to wire flexing and exceeded the requirements that a connector must meet in order to gain acceptance by that organization.

FIG. 7 illustrates a barrel shaped connector 66 having four channels 26. This style of connector illustrates the versatility of the present invention. Of course, connector 66 will accommodate any number'of channels 26.

FIGS. 8, 9, and 10 show an embodiment of connector 16, herein designated as 16a, wherein floor 30 contains an insulation-piercing projection 68. Wire 10 is pressed into channel 26 without stripping backinsulation 12. As the wire is pressed in, edges 32 'cutinto insulation 12 and the two free ends, 70-72, of the insulation are peeled over top surfaces 34 and down the outside of sidewalls 28 by die member 44. The conductor 14 enters channel 26 with projection 68 piercing insulation 12. The remnants 74 of the pierced insulation are loosely pressed down into grooves 75 defined by projection 68 and sidewalls 28. By lying loosely in grooves 75, remnants 74 may expand with any temperature increases without placing pressure against the connection. Insulation 12 on top of the connection (FIGS. 9 and 10) exhibits a depressed area 76 from contact with anvil 42 which as noted above has a width preferably less than the top opening to channel 26.

FIG. 11 illustrates a connection 80 wherein a solid conductor 14 has been tamped on top of a multistranded conductor 82. To accommodate multistranded conductor 82 the channel, herein designated as 26a, is modified to a circular shape up to the upper portions, designated as 84, where the sides assume the generally trapezoidal shape of channel 26 seen in FIG. 3; Le, they are positioned from about 70 to 80 relative to the horizontal. The height of upper portion 84, designated by the small letter 11 in FIG. 11, is sized so that preferably about 85 percent of the conductor 14 will be accommodated within channel 26a.

Another modification shown in FIG. 11 of connector 16b is the presence of exterior grooves 86. The grooves permit connector 16b to be held by corresponding splines (not shown) in the tool member (not shown). This is required as the operator must insert multistranded conductor 82 into channel 260 from one or the other end.

FIG. 12 illustrates a connection wherein a con ductor 14-is connected to a flat foil conductor 92 in channel 26b in connector 160. To accommodate the foil conductor, a modification is made to the connector; i.e., one sidewall 28 extends upwardly at 90 relarive to the floor of the channel. It is against this sidewall, designated 28a in FIG. 12, that foil conductor 92 is positioned. FIG. 12 also shows where conductor 14 has been tamped completely within the confines of channel 26b as defined by the sidewalls; i.e., there is no crown 36. Illustrated in FIG. 13 is a connector 16 as described in FIGS. 1-3 receiving a smaller conductor 14. As in FIG. 12, conductor 14 has been completely tamped into connector 16.

FlGS. 14a and b illustrate a connection between connector l6 and a multi-stranded conductor 94. FIG. 140 shows the positioning of conductor 94 within channel 26 prior to being tamped therein by anvil 42. FIG. 14b illustrates the completed connection.

FIG. 15 illustrates the connector, herein designated 16d, wherein floor contains a stranded wire divider 96. By means of this divider, a joint terminationconnection with and between a stranded copper fixture wire 98 and conductor 14 is achieved with extremely good results. One reason therefore is that as conductor 14 is tamped down into channel 26, it forces the copper wires over the edges 100 of divider 96 and thereby cleaning or scouring the wires. Another wiping action occurs at the interface 102 between the strands of wire 98 and conductor 14. The scouring and wiping actions create two conductive paths; one is the direct path be tween conductor 14 and wires 98: the second path is an indirect path that goes from the copper wires 98 through the connector 16d and into conductor 14 at point 104 on the walls of channel 26. Point 104 is that general point where maximum wiping between sidewall 28 and conductor 14 occurs.

In summary the present invention discloses a novel means of terminating or connecting aluminum conductors to aluminum connectors. For example, of the novel features, the transitional zone is one which enhances the use of the present invention to unstable environments; i.e., where such connections are subject to frequent vibrations and movements.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as some modifications will be obvious to those skilled in the art.

What is claimed is:

1. An electrical connection between an aluminum terminal and an aluminum conductor comprising:

a. an elongated aluminum terminal member having an axially extending channel defined by a floor and sidewalls extending upwardly from either side of the floor wherein the sidewalls thereof converge inwardly away from the floor, the degree of convergence being about to about relative to the floor, said floor containing an insulation piercing projection adapted to cut into and peel back insulation which may be present on an aluminum conductor; and

b. a length of insulated aluminum conductor deformably pressed into said channel wherein said projection pierced through the insulation, peeling such away and wherein a single transitional zone adapted to eliminate internal stress in the aluminum conductor adjacent said aluminum terminal includes a gradual change from the deformed length of said aluminum conductor to the nondeformed aluminum conductor extending up to the aluminum terminal. 

1. An electrical connection between an aluminum terminal and an aluminum conductor comprising: a. an elongated aluminum terminal member having an axially extending channel defined by a floor and sidewalls extending upwardly from either side of the floor wherein the sidewalls thereof converge inwardly away from the floor, the degree of convergence being about 70* to about 80* relative to the floor, said floor containing an insulation piercing projection adapted to cut into and peel back insulation which may be present on an aluminum conductor; and b. a length of insulated aluminum conductor deformably pressed into said channel wherein said projection pierced through the insulation, peeling such away and wherein a single transitional zone adapted to eliminate internal stress in the aluminum conductor adjacent said aluminum terminal includes a gradual change from the deformed length of said aluminum conductor to the non-deformed aluminum conductor extending up to the aluminum terminal. 